Stand alone control module

ABSTRACT

A stand-alone control module for use in closed-wound drainage systems is described. The control module transforms a variable high-vacuum source into a constant low-vacuum source. The control module also provides a one-way check valve to prevent return of air to a patient when draining such air from the pleural cavity of the patient. The control module is a water-based control module. It includes a first-suction control chamber for transforming a variable high-vacuum into a constant low-vacuum. The first chamber contains a first column of fluid at a first pre-determined level. The module also includes a second water seal chamber that contains a second column of fluid at a second pre-determined level. The height of the second column of fluid is less than the height of the first column of fluid. Tubes are placed in each chamber that have one end of each tube located below the columns of fluid. The column of fluid within the first chamber acts to regulate the vacuum within the chambers and the column of fluid in the second chamber provides a one-way check valve to prevent air from returning to the patient.

FIELD OF THE INVENTION

This invention relates generally to vacuum regulating systems andone-way check valves and more specifically relates to water-based vacuumregulating systems and one-way check valves for closed-wound drainageapplications.

BACKGROUND OF THE INVENTION

In the medical field it is frequently necessary after surgery or after apatient has incurred a trauma to the chest cavity to collect fluids fromthe chest cavity after the cavity has been closed. This type of fluidcollection is commonly referred to as "closed-wound drainage". Oneparticularly important feature of closed-wound drainage is that itrequires a relatively low vacuum to suction fluids from the patient'schest cavity. If higher vacuums are used, damage to the internal organsmay occur. Typical vacuum ranges of between 20-30 cm. H₂ O are used tocollect fluids from a closed chest or pleural cavity. However, in mosthospitals, the vacuum sources commonly available are in the range of0-760 mm. Hg. Most hospitals provide such vacuum sources on the wallnext to a patient's bed. It is therefore necessary to provide a systemwhich converts a relatively high vacuum provided by the hospital to arelatively low vacuum for use in closedwound drainage systems. It hasbeen found that the vacuum source provided at a patient's bedside inmany hospitals may also be a variable pressure vacuum source. With suchsources, the vacuum provided may vary unexpectedly. Therefore, a needexists to provide a system which will not only convert a relatively highvacuum to a low vacuum but will also maintain a relatively constantvacuum despite fluctuations that may occur in the high vacuum source.

Another need exists in draining fluids and gases from a patient'spleural cavity in that it is important that as the gases are removedfrom a patient that they are not inadvertently returned to the patient.Typically, in a closed-wound drainage system, a small amount of gas isremoved from the patient's pleural cavity with each inhalation of thepatient. If the patient's lung is collapsed, each time a small amount offluid and gas is removed from the patient's pleural cavity, thepatient's lung is allowed to expand by the amount of fluid or gas thatis removed. Thus, the patient's lung will typically gradually expandover a period of several days if the lung has entirely collapsed. Duringthis process, it is important to make sure that gases are notinadvertently returned to the patient which would cause the lung tore-collapse.

Air may be inadvertently returned to a patient's pleural cavity when itis necessary to transport a patient from one location to another. When apatient is transported, it is frequently necessary to disconnect thepatient from a vacuum source that is fixed in the wall of a hospital.The patient is then allowed to drain fluids from the pleural cavityusing only gravity. Under such conditions, fluid will continue to drain,but air may return to the patient if air is present within theclosed-wound drainage system. Therefore, it is necessary to provide aone-way check valve to prevent such return of air. One object of thepresent invention is to provide such a one-way check valve in astand-alone module.

Another object of the invention is to provide a water-based stand-alonemodule which can be used not only for pleural wound drainage systems,but can be also be used for other drainage applications such as knee andhip surgery.

SUMMARY OF THE INVENTION

A stand-alone control module for transforming a variable high-vacuumsource into a constant low-vacuum source for medical applications isdescribed. The module also provides a one-way check valve to prohibitreturn of air when draining fluids and air from the pleural cavity of apatient. The module includes a first-suction control chamber fortransforming a variable high-vacuum into a constant low vacuum. Thefirst chamber contains a first column of fluid at a first pre-determinedlevel. A second water-sealed chamber is also provided for containing asecond column of fluid at a second pre-determined level. The secondlevel is less than the first level. A lid is also provided for coveringan upper surface of both the first and second chambers. The lid providesa first path between a high-vacuum source and the second chamber. Thelid also provides a second path connecting the first and second chambersabove the fluid levels thereby equalizing the pressure in the first andsecond chambers. A first tube is provided within the first chamber. Thefirst tube has first and second ends. The first end of the first tube isimmersed in the fluid in the first chamber. The second end of the firsttube extends above the first chamber through the lid and is open toatmospheric pressure. Thus, when a high-vacuum source is applied to thefirst chamber through the second pathway, the first tube suppliesatmospheric air pressure to the high-vacuum source through the firstcolumn via bubbles in the first column of fluid thereby creating aresidual pressure in the first chamber which remains constant anddependent on the height of the column of fluid in the first chamber.

The module also includes a second tube within the second chamber. Thesecond tube also has first and second ends. The first end of the secondtube is immersed in the fluid in the second chamber and the second endof the tube is in communication with the pleural cavity of a patient.The vacuum in the second chamber is normally lower than the vacuum inthe patient's pleural cavity. This causes air in the cavity to be pulledthrough the second end of the second tube through the second column offluid towards the high-vacuum source. When the vacuum in the cavity isgreater than the vacuum in the second chamber, fluid in the secondchamber is pulled into the second tube to prevent air in the secondchamber from returning to the pleural cavity. The second tube includes avalve located at the second end which closes when fluid rises to thesecond end of the tube.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of the preferred embodiment of aclosed-wound drainage autotransfusion system;

FIG. 2 is a perspective view of a liner and cannister of the preferredembodiment of the invention as the liner is inserted into the cannister;

FIG. 3 is a side view of a liner;

FIG. 4 is a perspective view of the preferred cannister and liner;

FIG. 5 is a perspective view of a re-usable cannister showing a vacuumconnection to the cavity of the cannister;

FIG. 6 is a cut-away view of the control module taken along lines 6--6in FIG. 7;

FIG. 7 is a top view of the control module;

FIG. 8 is a side view of a valve used in the preferred embodiment of theinvention;

FIG. 8 is a front view of the valve illustrated in FIG. 8;

FIG. 10 is an illustration of a drainage straw used in one embodiment ofthe invention;

FIG. 11 is a perspective view of a tray for storing and transporting acontrol module; and

FIG. 12 is a perspective view of a control module located in the tray ofFIG. 11 in the upright position to allow fluid to be added to thecontrol module.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

Refer now to FIG. 1 which is a perspective view of the preferredembodiment of a closed-wound drainage autotransfusion system 10. As canbe seen in the figure, the system 10 includes a cannister 12 and acontrol module 14. The cannister is located in a hanger 16. The controlmodule 14 is also mounted on the hanger 16. The cannister 12 includeswalls 18 which form a cavity 20 as can be seen in FIG. 2. The systemincludes a hollow liner 22 for insertion into the cavity 20 of thecannister. The purpose of the liner 22 is to receive fluids and gasesfrom the pleural cavity of the patient. The liner 22 includes a cover 24that is attached to the top 26 of the liner 22. The cover 24 and liner22 are sealed to one another to form a fluid and gas-tight seal. Thecover 24 can be attached to the top 28 of the cannister 12 as can beseen in FIG. 1.

Referring now to FIG. 3, the liner 22 includes a flexible body 30. Theflexible body 30 has upper and lower portions 32 and 34. The upperportion 32 is attached to the cover 24. The lower portion 30 is attachedto a bottom 36. The flexible body 30 and the bottom 36 are shaped so asto generally conform to the walls 18 of the cannister 12. Therefore,when the flexible body 30 and the bottom 36 are inserted into the cavity20 as illustrated in FIG. 2, the liner 22 will fit snugly against thewalls 18 of the cavity 20 of the cannister 12 as illustrated in FIG. 4.

In the preferred embodiment, the system 10 includes a vacuum means forcontinuously providing a relatively high vacuum to the cavity 20 of thecannister 12 and a relatively low vacuum inside the liner 22 when theliner 22 is located in the cavity 20 to cause the liner to expandagainst the walls 18 of the cannister 12. The vacuum means includes a"T"-shaped port 38 as illustrated in FIG. 5. The port 38 includes alower leg 40 which can be connected to a high-vacuum source. Thehigh-vacuum source is typically a vacuum-source provided in the wall ofa hospital next to a patient's bed. In many hospitals, this source ofhigh-vacuum tends to provide a vacuum in the range of 0-760 mm. Hg. Thisvacuum may vary unexpectedly. However, the vacuum is generallysufficient to cause the flexible body 30 to expand against the walls 18of the cannister 12 when the vacuum is applied through a middle leg 42of the "T"-shaped port 38. The middle leg 42 is in fluid communicationwith the cavity 20 of the cannister 12 to allow the high vacuum sourceto be applied to the cavity 20. The "T"-shaped port 38 also includes anupper leg 44 which is attached to a braided tube 46 which will bediscussed in greater detail below.

The vacuum means which provides a relatively low vacuum to the inside ofthe liner 22 must provide this vacuum at a constant relatively lowlevel. The reason why the vacuum provided to the inside of the liner 22must remain constant is that variations in the vacuum in the liner aretransmitted to the patient 48 via a drainage tube 50 which is connectedto a chest tube 52 as illustrated in FIG. 1. Thus, if a high vacuum isapplied to the inside of the liner 22 the same vacuum will be applied tothe chest cavity of the patient 48. This can injure the patient'sinternal organs. Also, variations in vacuum can injure the patient'sorgans even if the vacuums are relatively low. Therefore, the highvacuum present in braided tube 46 is transmitted into control module 14for transforming the variable high vacuum into a constant low vacuum.The control module 14 is illustrated in greater detail in FIG. 6.

As can be seen in FIG. 6, the control module 14 includes a first suctioncontrol chamber 54 for transforming the variable high vacuum into aconstant low vacuum. When the module 14 is in use, the chamber 54 ispartially filled with a sterile fluid 56. The first chamber 54 include afirst tube 58 that is located within the first chamber 54. The firsttube has first and second ends 60 and 62. The first end 60 is theimmersed in fluid 56 and the second end 62 extends above the top of thefluid 56 in the first chamber. The second end 62 is attached to a lid 66which covers the top 64 of the first chamber 54. The lid 66 includes aport 68 which is located immediately above the top 64 of the firstchamber 54. The second end 62 of the first tube 58 is in sealedengagement with the port 68. The port is partially covered by a cap 70.A narrow air space 72 exists between the cap 70 and the port 68 to allowatmospheric air pressure into tube 58. The high-vacuum source present inbraided tube 46 is attached to a cap 74 which is located on ahigh-vacuum port 76 on lid 66. The port 76 provides a first path 78between the high-vacuum source and a second chamber 80 in the controlmodule 14. The lid 66 and the control module 14 are shaped in such a waythat when the lid 66 is placed on the control module 14 a second path 82is formed between the first and second chambers 54 and 80. The secondpath is a relatively narrow path that provides fluid communicationbetween the first and second chamber 54 and 80. Thus, the high vacuumprovided to the second chamber 80 through port 76 is also transmitted tothe first chamber 54. The high vacuum causes atmospheric air present intube 58 to be pulled through the first end 60 of the tube against thefirst column 56 of fluid. The resistive force of the water pressureagainst the air as it is drawn through the water column creates arelatively low back pressure which is proportional to the height of thecolumn of water. This reduces the vacuum present in the upper portion ofthe chamber 54 to a relatively low, constant vacuum which can becontrolled simply by controlling the height of the column of fluid.Therefore, the first chamber 54 acts as a pressure regulator whichtransforms a variable high vacuum into a constant relatively low vacuum.

The control module 14 includes a second chamber 80 which provides awater-based one-way check valve. This chamber will now be discussed ingreater detail. The chamber 80 includes a second tube 84 which islocated within the chamber. The second tube 84 includes first and secondends 86 and 88. The first end 86 is immersed in sterile fluid when themodule 14 is in use. In the preferred embodiment, the second chamber 80is partially filled with 2 cm. high of sterile fluid. The second end 88of the second tube 84 is attached to a vacuum-interface port 80 on lid66. The vacuum-interface port 80 is located over the upper portion 82 ofthe second chamber 80. The vacuum-interface port 80 has one end 84connected to a vacuum-interface tube 86 which will be discussed ingreater detail below. The vacuum-interface tube 86 is in fluidcommunication with the inside of the liner 22. As discussed above, thevacuum present within the liner 22 is in fluid communication with thecavity of a patient 48 through tubes 50, 52. Therefore, the vacuumpresent in the first and second chambers 54, 80 of the control module 14is also the same vacuum that is provided to the cavity of the patient48.

The purpose of the second chamber 80 of the control module 14 is toprovide a one-way fluid-based check valve to prevent gases from beingdelivered to the cavity of a patient 48. As will be discussed in greaterdetail below, gases are allowed to travel downwardly through the secondtube 84, but are not allowed to travel from the upper portion 82 of thesecond chamber 80 through tube 84. As discussed above, the secondchamber 80 includes a second column of fluid 88 which is 2 cm. high inthe preferred embodiment of the invention. The second column of fluid 88acts to prevent gas present in the upper portion 82 of the secondchamber 80 from entering the first end 86 of the second tube 84 in theevent that the pressure in the upper portion 82 of the second chamber 80is greater than the pressure in the patient's cavity. The pressure inthe upper portion 82 of the second chamber may be greater than thepressure in the patient's cavity when the system 10 is disconnected froma high-vacuum source. In this event, the pressure and the upper portion82 of the second chamber 80 will rise to atmospheric pressure. If fluidis not present in the second chamber 80, this atmospheric pressure canbe transmitted too the patient's cavity causing the patient's lung tocollapse. This is prevented by the presence of a second column of fluid88 and the second chamber 80. When the pressure in the upper portion 82of the chamber 80 is greater than the pressure in a patient's cavity,each exhalation of the patient will cause the fluid in the secondchamber 80 to be drawn up into the second tube 84 temporarily. The fluidthat is drawn up into the second tube 84 rises and falls with eachpatient inhalation and exhalation whenever the system 10 is disconnectedfrom a high-vacuum source. This fluid in the second tube 84 prevents anygas present in the second chamber from entering into the patient's chestcavity.

One feature of the control module 14 is that the first tube 58 includesa mesh net 100 covering the first end 60 of the first tube 58. Thepurpose of the mesh net 100 is to cause air drawn through the first tube58 into the first column 58 of fluid to be broken up into very finebubbles. This act of breaking the air into fine bubbles reducesturbulence in the first column 56 of fluid. This is important because itprevents splashing of fluid 56 in the first chamber into the secondchamber 80 through the second path 82.

As discussed above, the lid 66 and the upper portion 102 of the controlmodule between the first and second chambers 54, 80 forms the secondpath 82. In the preferred embodiment of the invention, the lid 66 andthe upper portion 102 of the control module 14 form a gap with oneanother that creates the second path 82. The entrance to the second path82 from the first chamber 54 in the preferred embodiment is no greaterthan 0.06 inches. The purpose of providing a very small entrance to thesecond path 82 from the first chamber 54 is to reduce the possibility offluid 56 in the first chamber 54 from entering the second chamber 80. Inthe preferred embodiment, the second path 82 is a narrow torturous path.As illustrated in FIG. 6, the path 82 is a "U"-shaped path formed by"U"-shaped portion 104 in the upper portion 102 of the control module 14which is parallel to a "U"-shaped portion 106 in lid 66.

As also illustrated in FIG. 6, the second end 88 of the second tube 84is attached to a vacuum-interface port 80. A float valve 108 is locatedinside the port 80. The float valve 108 includes an inverted rubber cup110 which is centered over the upper end 88 of the second tube 84. Asfluid in the second tube 84 reaches the inverted cup 110, the cup risesuntil a flexible gasket 112 located between the upper portion of the cup110 and the vacuum-interface port 84 causes the float valve 108 toclose.

One important feature of the preferred embodiment of the invention isthat the lid 66 includes at least one bleed orifice 114. In thepreferred embodiment of the invention, a bleed orifice 114 is locatedadjacent to the first path 78 on the lid 66. The purpose of the bleedorifice 114 is to transform the high-source vacuum into an intermediatelevel vacuum which can be further reduced to a low vacuum by the firstchamber 54 of the control module 14. By allowing small amounts of air toenter into the first and second chambers 54, 80 through the bleedorifice 114, the vacuum from the high-vacuum source is partiallyreduced.

The high vacuum from the high-vacuum source is also partially reducedthrough the use of an in-line orifice 116 located in the high-vacuum cap74. The relatively small in-line orifice 116 causes the high vacuum fromthe high-vacuum source to be reduced to a lower vacuum since the bleedorifice 114 pulls air into the upper portions of the first and secondchambers as a high vacuum is applied to the inline orifice 116.Therefore, the in-line orifice 116 and the bleed orifice 114 act inconjunction to produce an intermediate level vacuum which is thenreduced to a low vacuum as discussed above.

In the preferred embodiment of the invention, the first column of fluid56 in the first chamber 54 is formed using no greater than 220 cc offluid to provide 20 cm. H₂ O vacuum in the first and second chambers 54,80 when the high-vacuum source provides up to 14.7 psi vacuum to thefirst path 78. This is a relatively small amount of fluid compared toother systems used in the past. This small amount of fluid is able toprovide a reduction in vacuum due to the use of the bleed orifice 114and the in-line orifice 116 to step down the vacuum from the high-vacuumsource to an intermediate level vacuum.

Refer again to FIG. 1, as can be seen in this figure in the preferredembodiment of the invention, a vacuum-sensing valve 118 is provided inseries between the low-vacuum source 120 of the control module 14 andthe inside 122 of the liner 22. The valve is designed to open the insideof the liner to atmospheric pressure when the vacuum inside 122 theliner 22 exceeds a pre-determined value. In the preferred embodiment ofthe invention, the pre-determined value is 40 cm. H₂ O. This preventsundesirably high vacuums from being applied to the patient's chestcavity. The valve 118 will now be described in greater detail. Refer nowto FIG. 8, which is a cut-away view of the vacuum-sensing valve 118. Thevalve includes a valve body 124, a seat 126 and an elastomeric umbrella128. As can be seen in FIG. 8, the seat 126 of the vacuum-sensing valve118 includes a plurality of openings 130 to allow atmospheric air toenter the valve body 124 when the vacuum within the valve body exceeds apre-determined level. When the vacuum exceeds this pre-determined level,the edges 132 of the elastomeric umbrella 128 will be drawn toward thecenter of the valve body 124 and away from the valve seat 126. When theedges 132 of the elastomeric umbrella 128 are in their normal position,the edges 132 are biased against the openings 130. However, when thevacuum exceeds the pre-determined level, as discussed above, the edgeswill withdraw into the valve body 124 to allow atmospheric air into thevalve body. This prevents undesirably high vacuums which may be presentinside the liner 122 to be applied to the chest cavity of a patient.

Refer now to FIG. 1. One important feature of the invention is that thesystem 10 includes a drainage means 134 for providing fluidcommunication between the inside of the liner 122 and the chest cavityof the patient 48. In the preferred embodiment of the invention, thedrainage means 134 includes a drainage tube 50 which is connected to apatient port 136 and the cover 24 of the system 10. The patient port 136has a porous filter 138 attached to collect large particle-size debriswhich may be drawn into the system from the patient's chest cavity. Thisfilter prevents this degree from being mixed with fluid that iscollected in the liner 22 for later re-infusion back into the patient.In the preferred embodiment of the invention, the filter has a pore sizeof between 120 and 130 microns. The filter is located inside the liner22 immediately under the patient port 136.

In the preferred embodiment of the invention, the cover 24 also includesan interface port 140 to allow removal of fluids from the liner 22 forfurther processing or re-infusion back into the patient without removingthe liner from the cannister. When the interface port 140 is not in use,the port is covered with a cap 142. In the preferred embodiment of theinvention, a sterile straw 144 is inserted into the liner 22 to withdrawfluids from the bottom of the liner. The straw is illustrated in FIG. 10in its pouch.

The straw 144 has first and second ends 146, 148. The first end of thestraw can be inserted through the interface port 140 down into thebottom of the liner 22. The second end 148 of the straw 144 is attachedto an elbow 150. The elbow includes first and second ends 152, 154. Thefirst end of the elbow includes a skirt 156 which is designed to fitsnugly around the outside diameter of the interface port 140 to firmlysecure the straw onto the interface port 140. Accordingly, the skirt 156consists of a ring which can be concentrically placed about theinterface port 140. The second end 154 of the elbow 150 has a taperedport for connection to tubing of various inside diameters. This port isnormally attached to such tubing to allow fluid within the liner to bedrawn into the tubing either for re-infusion back into the patient orfor further processing. For example, in some instances, it may bedesirable to sent the fluid through a cell washer to remove the redcells from the fluid and discard any other debris that may be present inthe fluid. The red cells may then be used by the patient.

Thus, it is important for the straw 144 to be maintained in a sterilecondition prior to insertion into the liner 22, It is also importantthat the medical personnel be able to insert the straw 144 into theliner 22 without compromising its sterility. Therefore, one feature ofthis invention is to provide a sterile system in which the straw ismaintained in a sterile, thin-walled flexible sleeve 158 prior toinsertion into the liner 22. As can be seen in FIG. 10, the sleevecompletely covers the straw. The sleeve has first and second ends 160and 162. In the preferred embodiment, the ends are simply folded inwardtowards the sleeve and taped shut. In one embodiment of the invention,medical personnel can open the first end 160 of the sleeve 158 to exposethe first end 146 of the straw 144. The first end 160 of the sleeve 158can be pushed back toward the elbow to allow the first end 146 of thestraw 144 to be inserted into the liner 22 while the second end 148 ofthe straw remains covered by the sleeve 158. After the straw has beeninserted, the sleeve can be completely removed to allow the second end154 of the elbow 150 to be attached to a tube as discussed above. Inanother embodiment of the invention the first end 160 of the sleeve 158is opened simply by forcefully puncturing the sleeve with the first end146 of the straw 144.

In order to insure that the straw 144 is transported in a sterilecondition, the entire sleeve 158 is enclosed in an outer peelable outerpouch 164. The outer pouch can be opened by a "non-sterile" medicalpersonnel to present the sterile sleeve 158 and straw 144 to a "sterile"nurse.

Refer now to FIG. 11 which is a perspective view of a tray 166 used tostore and transport the control module 14. The tray 166 includes astorage means 168 for maintaining the control module 14 in a horizontalposition within the tray as the module is being transported. The tray166 also includes a holding means 170 for maintaining the control module14 in a vertical position in the tray 168 to allow the control module 14to be partially filled with sterile fluid. This is illustrated in FIG.12. In the preferred embodiment of the invention, the holding meansincludes a pair of indentions 172 which form a slot 174 for maintainingthe control module 14 in a vertical position. In the preferredembodiment, the storage means 168 is a pre-formed plastic container 176having a top opening 178 that is sealed with a lid 180 which can bepeeled away from the top opening to expose the inside of the container176. In the preferred embodiment, the preformed container 176 includes abottom and side walls which generally conform to the overall outer shapeof the control module 14 when the control module 14 is in a horizontalposition. Thus, the control module 14 can be snugly placed inside thecontainer 176 to be transported.

The tray 166 described herein has several advantages. First, the use ofthe tray to maintain the control module in an upright position as themodule is being filled acts as a sterile field around the control modulesince the inside of the tray is sterile prior to peeling back the lid180 from the top 178 of the tray. Second, the tray 166 acts as a fluidcollection means to collect any spills which may occur as the module isbeing filled. This is of great value to operating room personnel.

I claim:
 1. A stand-alone control module for transforming a variablehigh vacuum source into a constant low vacuum source for medicalapplications and for providing a one-way check valve to prohibit returnof air when draining fluids and air through a drainage tube having afirst end located in the plural cavity of a patient comprising:a firstchamber containing a first column of fluid having a height at a firstpredetermined level; a second chamber containing a second column offluid at a second predetermined level, said second level being less thansaid first level; a lid covering an upper surface of both of said firstand second chambers, said lid having a first port for connecting saidsecond chamber to a high vacuum source, said lid providing a connectingpathway connecting said first and second chambers above said fluidlevels in said first and second chambers thereby equalizing a pressuredifferential between said first and second chambers, a first tube withinsaid first chamber, said first tube having first and second ends, saidfirst end of said first tube being immersed in said first column offluid and said second end of said first tube extending above said firstchamber through said lid and being open to atmospheric pressure, wherebywhen said high vacuum source is applied to said first chamber throughsaid connecting pathway, said first tube supplies atmospheric air tosaid first chamber through said first column of fluid via bubblesthereby creating a residual pressure in said first chamber which remainsconstant and dependent on the height of said first column of fluid insaid first chamber, said first end of said first tube having a mesh netcovering said end to break up air in said tube into fine bubbles beforeentering said first fluid column to reduce turbulance and noise in saidfirst chamber; and a second tube within said second chamber, said secondtube having first and second ends, said first end of said second tubebeing immersed in said second column of fluid in said second chamber andsaid second end of said second tube being connected to said second endof said drainage tube to be in communication with the plural cavity ofthe patient, said second chamber having a vacuum which is normally lowerthan a vacuum in the patient's pleural cavity thereby causing air in thepleural cavity to be pulled through said second end of said second tubethrough said second column of fluid toward said high vacuum source, whensaid vacuum in said pleural cavity is greater than vacuum in the secondchamber, fluid in said second chamber is pulled into said second tube toprevent air in said second chamber from returning to said pleuralcavity, said second tube having a valve located at said second end whichcloses when said second fluid column rises to said second end of saidtube.
 2. A control module as recited in claim 1 wherein said first portin said lid further includes a cap having an air flow restrictor betweensaid first path and said high vacuum source to cause a drop in vacuumbetween said high vacuum source and said second chamber, said lid alsohaving at least one bleed orifice to atmosphere and at least one of saidfirst and second chambers, said bleed orifice also causing an additionaldrop in vacuum in said chambers to prevent excessive bubbling in saidfirst chamber when said high vacuum source is providing maximum vacuum.3. A control module as recited in claim 2 wherein said bleed orifice islocated adjacent said first port on said lid.
 4. A control module asrecited in claim 1 wherein said valve is a float valve having a rubbergasket surrounding said second wherein said valve seals said second endof said second tube when fluid in said second tube rises to said secondend.
 5. A control module as recited in claim 1 wherein said connectingpathway between said first and second chambers in said lid is a narrowtorturous pathway to prevent fluid in said first chamber from splashinginto said second chamber.
 6. A control module as recited in claim 5wherein said connecting pathway has an entrance into said first chamberof no greater than 0.060".
 7. A control module as recited in claim 5wherein said connecting pathway has an entrance into said first chamberof between 0.040" and 0.125".
 8. A control module as recited in claim 1wherein said mesh net has a mesh openings in the range of 0.010" to0.015".
 9. A control module as recited in claim 1 wherein said firstfluid column is formed using no greater than 220 cc of fluid to provide20 cm H₂ O vacuum in said first and second chambers when said highvacuum source provides up to 14.7 psi vacuum to said first path.